Object format resilient to remote object store errors

ABSTRACT

Techniques are provided for remote object store error handling. A storage system may store data within one or more tiers of storage, such as a local storage tier (e.g., solid state storage and disks maintained by the storage system), a remote object store (e.g., storage provided by a third party storage provider), and/or other storage tiers. Because the remote object store may not provide the same data consistency and guarantees that the storage system provides for clients such as through the local storage tier, additional validation is provided by the storage system for the remote object store. For example, when data is put into an object of the remote object store, a verification get operation is performed to read and validate information within a header of the object. Other verifications and checks are performed such as using a locally stored metafile to detect corrupt or lost metadata and/or objects.

BACKGROUND

Many storage systems may provide clients with access to data storedwithin a plurality of storage devices. For example, a storage controllermay store client data within a set of storage devices that are locallyaccessible (e.g., locally attached to the storage controller) orremotely accessible (e.g., accessible over a network). A storageaggregate of storage may be generated from the set of storage devices(e.g., the storage aggregate may be stored across multiple storagedevices). The storage aggregate may be exported from a storage filesystem to a client. The storage aggregate may appear as a single storagecontainer to the client, such as a volume or logical unit number (lun).In this way, the storage aggregate abstracts away the details, from theclient, of how the storage aggregate is physically stored amongst theset of storage devices.

Some storage systems may store data within a multi-tiered storagearrangement. For example, the storage controller may store data within ahard disk drive tier and a solid state storage tier. The hard disk drivetier may be used as a capacity tier to store client data and forprocessing input/output operations. The solid state storage tier may beused as a cache for accelerating the processing of storage operations.Unfortunately, different storage tier have different characteristics andbehaviors, which can affect performance and guarantees provided toclients by a storage system.

In an example, a storage system may utilize a local storage tier and aremote third party storage tier as two of the storage tiers within whichthe storage system stores data. The storage system may be able toprovide high availability, security, data consistency, data protection,and/or other guarantees using the local storage tier because the storagesystem may manage and control the local storage tier. However, thestorage system may be unable to provide similar guarantees, such as thatdata is properly stored, managed, is consistent, and is accurate, toclients for the remote third party storage tier because the storagesystem does not manage and control the remote third party storage tier.For example, new data could be written to the remote third party storagetier. When reading the new data, old data or no data could be returnedby the remote third party storage tier due to delay. Thus, the storagesystem may be unable to provide the same level of enterprise guaranteeswhen working with the remote third party storage tier as backendstorage.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a component block diagram illustrating an example clusterednetwork in accordance with one or more of the provisions set forthherein.

FIG. 2 is a component block diagram illustrating an example data storagesystem in accordance with one or more of the provisions set forthherein.

FIG. 3 is a flow chart illustrating an exemplary method of remote objectstore error handling.

FIG. 4 is a component block diagram illustrating an exemplary computingdevice for remote object store error handling, where an object comprisesa header and one or more object pages.

FIG. 5 is a component block diagram illustrating an exemplary computingdevice for remote object store error handling, where a put operation anda subsequent verification get operation are performed.

FIG. 6A is a component block diagram illustrating an exemplary computingdevice for remote object store error handling, where a metafile is usedto validate and locate an object.

FIG. 6B is a component block diagram illustrating an exemplary computingdevice for remote object store error handling, where a volume moveoperation is performed.

FIG. 7 is a component block diagram illustrating an exemplary computingdevice for remote object store error handling, where I/O throughput isdynamically adjusted based upon latency of a remote object store.

FIG. 8 is a component block diagram illustrating an exemplary computingdevice for remote object store error handling, where a sequence numberis invalidated.

FIG. 9 is a component block diagram illustrating an exemplary computingdevice for remote object store error handling, where an object isinvalidated.

FIG. 10 is an example of a computer readable medium in accordance withone or more of the provisions set forth herein.

DETAILED DESCRIPTION

Some examples of the claimed subject matter are now described withreference to the drawings, where like reference numerals are generallyused to refer to like elements throughout. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of the claimed subject matter. It maybe evident, however, that the claimed subject matter may be practicedwithout these specific details. Nothing in this detailed description isadmitted as prior art.

One or more techniques and/or computing devices for remote object storeerror handling are provided herein. A storage system may utilizemultiple tiers of storage to store client data. For example, the storagesystem may utilize a local storage tier (e.g., a performance storagetier, such as a solid state storage tier or a hard disk drive storagetier), a remote object store tier (e.g., a distributed network ofstorage provided by a third party provider, cloud storage, etc.), and/orother tiers of storage.

Unfortunately, the remote object store tier may not provide adequateguarantees of data validity and consistency that the storage systemguarantees for clients. For example, a remote object store may returnold data instead of newly written data due to delays. In anotherexample, the remote object store may return an object not found responsefor the newly written data due to delays. Accordingly, as providedherein, remote object store error handling is provided by the storagesystem for the remote object store. In particular, validation isprovided to ensure that data written to the remote object store isassociated with a correct object. Validation is also provided to ensurethat metadata corruption due to disk failure does not result inincorrect data being served to clients (e.g., corruption of locallystored metadata that would otherwise direct client requests to incorrectobjects within the remote object store). Validation is also providedthat data served from the remote object store is verified before beingused to service client requests, such as read requests. Validation isalso provided to detect intermittent errors from the remote objectstore, and to perform adaptive retries of operations to the remoteobject store. Validation is also provided to track and avoid sending I/Ooperations for lost blocks due to lost metadata (e.g., locally storedmetadata used to locate and access objects within the remote objectstore) or due to lost objects within the remote object store.

To provide for remote object store error handling, FIG. 1 illustrates anembodiment of a clustered network environment 100 or a network storageenvironment. It may be appreciated, however, that the techniques, etc.described herein may be implemented within the clustered networkenvironment 100, a non-cluster network environment, and/or a variety ofother computing environments, such as a desktop computing environment.That is, the instant disclosure, including the scope of the appendedclaims, is not meant to be limited to the examples provided herein. Itwill be appreciated that where the same or similar components, elements,features, items, modules, etc. are illustrated in later figures but werepreviously discussed with regard to prior figures, that a similar (e.g.,redundant) discussion of the same may be omitted when describing thesubsequent figures (e.g., for purposes of simplicity and ease ofunderstanding).

FIG. 1 is a block diagram illustrating the clustered network environment100 that may implement at least some embodiments of the techniquesand/or systems described herein. The clustered network environment 100comprises data storage systems 102 and 104 that are coupled over acluster fabric 106, such as a computing network embodied as a privateInfiniband, Fibre Channel (FC), or Ethernet network facilitatingcommunication between the data storage systems 102 and 104 (and one ormore modules, component, etc. therein, such as, nodes 116 and 118, forexample). It will be appreciated that while two data storage systems 102and 104 and two nodes 116 and 118 are illustrated in FIG. 1, that anysuitable number of such components is contemplated. In an example, nodes116, 118 comprise storage controllers (e.g., node 116 may comprise aprimary or local storage controller and node 118 may comprise asecondary or remote storage controller) that provide client devices,such as host devices 108, 110, with access to data stored within datastorage devices 128, 130. Similarly, unless specifically providedotherwise herein, the same is true for other modules, elements,features, items, etc. referenced herein and/or illustrated in theaccompanying drawings. That is, a particular number of components,modules, elements, features, items, etc. disclosed herein is not meantto be interpreted in a limiting manner.

It will be further appreciated that clustered networks are not limitedto any particular geographic areas and can be clustered locally and/orremotely. Thus, in one embodiment a clustered network can be distributedover a plurality of storage systems and/or nodes located in a pluralityof geographic locations; while in another embodiment a clustered networkcan include data storage systems (e.g., 102, 104) residing in a samegeographic location (e.g., in a single onsite rack of data storagedevices).

In the illustrated example, one or more host devices 108, 110 which maycomprise, for example, client devices, personal computers (PCs),computing devices used for storage (e.g., storage servers), and othercomputers or peripheral devices (e.g., printers), are coupled to therespective data storage systems 102, 104 by storage network connections112, 114. Network connection may comprise a local area network (LAN) orwide area network (WAN), for example, that utilizes Network AttachedStorage (NAS) protocols, such as a Common Internet File System (CIFS)protocol or a Network File System (NFS) protocol to exchange datapackets, a Storage Area Network (SAN) protocol, such as Small ComputerSystem Interface (SCSI) or Fiber Channel Protocol (FCP), an objectprotocol, such as S3, etc. Illustratively, the host devices 108, 110 maybe general-purpose computers running applications, and may interact withthe data storage systems 102, 104 using a client/server model forexchange of information. That is, the host device may request data fromthe data storage system (e.g., data on a storage device managed by anetwork storage control configured to process I/O commands issued by thehost device for the storage device), and the data storage system mayreturn results of the request to the host device via one or more storagenetwork connections 112, 114.

The nodes 116, 118 on clustered data storage systems 102, 104 cancomprise network or host nodes that are interconnected as a cluster toprovide data storage and management services, such as to an enterprisehaving remote locations, cloud storage (e.g., a storage endpoint may bestored within a data cloud), etc., for example. Such a node in theclustered network environment 100 can be a device attached to thenetwork as a connection point, redistribution point or communicationendpoint, for example. A node may be capable of sending, receiving,and/or forwarding information over a network communications channel, andcould comprise any device that meets any or all of these criteria. Oneexample of a node may be a data storage and management server attachedto a network, where the server can comprise a general purpose computeror a computing device particularly configured to operate as a server ina data storage and management system.

In an example, a first cluster of nodes such as the nodes 116, 118(e.g., a first set of storage controllers configured to provide accessto a first storage aggregate comprising a first logical grouping of oneor more storage devices) may be located on a first storage site. Asecond cluster of nodes, not illustrated, may be located at a secondstorage site (e.g., a second set of storage controllers configured toprovide access to a second storage aggregate comprising a second logicalgrouping of one or more storage devices). The first cluster of nodes andthe second cluster of nodes may be configured according to a disasterrecovery configuration where a surviving cluster of nodes providesswitchover access to storage devices of a disaster cluster of nodes inthe event a disaster occurs at a disaster storage site comprising thedisaster cluster of nodes (e.g., the first cluster of nodes providesclient devices with switchover data access to storage devices of thesecond storage aggregate in the event a disaster occurs at the secondstorage site).

As illustrated in the clustered network environment 100, nodes 116, 118can comprise various functional components that coordinate to providedistributed storage architecture for the cluster. For example, the nodescan comprise network modules 120, 122 and disk modules 124, 126. Networkmodules 120, 122 can be configured to allow the nodes 116, 118 (e.g.,network storage controllers) to connect with host devices 108, 110 overthe storage network connections 112, 114, for example, allowing the hostdevices 108, 110 to access data stored in the distributed storagesystem. Further, the network modules 120, 122 can provide connectionswith one or more other components through the cluster fabric 106. Forexample, in FIG. 1, the network module 120 of node 116 can access asecond data storage device by sending a request through the disk module126 of node 118.

Disk modules 124, 126 can be configured to connect one or more datastorage devices 128, 130, such as disks or arrays of disks, flashmemory, or some other form of data storage, to the nodes 116, 118. Thenodes 116, 118 can be interconnected by the cluster fabric 106, forexample, allowing respective nodes in the cluster to access data on datastorage devices 128, 130 connected to different nodes in the cluster.Often, disk modules 124, 126 communicate with the data storage devices128, 130 according to the SAN protocol, such as SCSI or FCP, forexample. Thus, as seen from an operating system on nodes 116, 118, thedata storage devices 128, 130 can appear as locally attached to theoperating system. In this manner, different nodes 116, 118, etc. mayaccess data blocks through the operating system, rather than expresslyrequesting abstract files.

It should be appreciated that, while the clustered network environment100 illustrates an equal number of network and disk modules, otherembodiments may comprise a differing number of these modules. Forexample, there may be a plurality of network and disk modulesinterconnected in a cluster that does not have a one-to-onecorrespondence between the network and disk modules. That is, differentnodes can have a different number of network and disk modules, and thesame node can have a different number of network modules than diskmodules.

Further, a host device 108, 110 can be networked with the nodes 116, 118in the cluster, over the storage networking connections 112, 114. As anexample, respective host devices 108, 110 that are networked to acluster may request services (e.g., exchanging of information in theform of data packets) of nodes 116, 118 in the cluster, and the nodes116, 118 can return results of the requested services to the hostdevices 108, 110. In one embodiment, the host devices 108, 110 canexchange information with the network modules 120, 122 residing in thenodes 116, 118 (e.g., network hosts) in the data storage systems 102,104.

In one embodiment, the data storage devices 128, 130 comprise volumes132, which is an implementation of storage of information onto diskdrives or disk arrays or other storage (e.g., flash) as a file-systemfor data, for example. In an example, a disk array can include alltraditional hard drives, all flash drives, or a combination oftraditional hard drives and flash drives. Volumes can span a portion ofa disk, a collection of disks, or portions of disks, for example, andtypically define an overall logical arrangement of file storage on diskspace in the storage system. In one embodiment a volume can comprisestored data as one or more files that reside in a hierarchical directorystructure within the volume.

Volumes are typically configured in formats that may be associated withparticular storage systems, and respective volume formats typicallycomprise features that provide functionality to the volumes, such asproviding an ability for volumes to form clusters. For example, where afirst storage system may utilize a first format for their volumes, asecond storage system may utilize a second format for their volumes.

In the clustered network environment 100, the host devices 108, 110 canutilize the data storage systems 102, 104 to store and retrieve datafrom the volumes 132. In this embodiment, for example, the host device108 can send data packets to the network module 120 in the node 116within data storage system 102. The node 116 can forward the data to thedata storage device 128 using the disk module 124, where the datastorage device 128 comprises volume 132A. In this way, in this example,the host device can access the volume 132A, to store and/or retrievedata, using the data storage system 102 connected by the storage networkconnection 112. Further, in this embodiment, the host device 110 canexchange data with the network module 122 in the node 118 within thedata storage system 104 (e.g., which may be remote from the data storagesystem 102). The node 118 can forward the data to the data storagedevice 130 using the disk module 126, thereby accessing volume 1328associated with the data storage device 130.

It may be appreciated that remote object store error handling may beimplemented within the clustered network environment 100. In an example,the node 108 and/or the node 118 may utilize a remote object storeand/or the data storage devices 128, 130 for serving client requests. Itmay be appreciated that remote object store erroring handling may beimplemented for and/or between any type of computing environment, andmay be transferable between physical devices (e.g., node 116, node 118,a desktop computer, a tablet, a laptop, a wearable device, a mobiledevice, a storage device, a server, etc.) and/or a cloud computingenvironment (e.g., remote to the clustered network environment 100).

FIG. 2 is an illustrative example of a data storage system 200 (e.g.,102, 104 in FIG. 1), providing further detail of an embodiment ofcomponents that may implement one or more of the techniques and/orsystems described herein. The data storage system 200 comprises a node202 (e.g., nodes 116, 118 in FIG. 1), and a data storage device 234(e.g., data storage devices 128, 130 in FIG. 1). The node 202 may be ageneral purpose computer, for example, or some other computing deviceparticularly configured to operate as a storage server. A host device205 (e.g., 108, 110 in FIG. 1) can be connected to the node 202 over anetwork 216, for example, to provide access to files and/or other datastored on the data storage device 234. In an example, the node 202comprises a storage controller that provides client devices, such as thehost device 205, with access to data stored within data storage device234.

The data storage device 234 can comprise mass storage devices, such asdisks 224, 226, 228 of a disk array 218, 220, 222. It will beappreciated that the techniques and systems, described herein, are notlimited by the example embodiment. For example, disks 224, 226, 228 maycomprise any type of mass storage devices, including but not limited tomagnetic disk drives, flash memory, and any other similar media adaptedto store information, including, for example, data (D) and/or parity (P)information.

The node 202 comprises one or more processors 204, a memory 206, anetwork adapter 210, a cluster access adapter 212, and a storage adapter214 interconnected by a system bus 242. The data storage system 200 alsoincludes an operating system 208 installed in the memory 206 of the node202 that can, for example, implement a Redundant Array of Independent(or Inexpensive) Disks (RAID) optimization technique to optimize areconstruction process of data of a failed disk in an array.

The operating system 208 can also manage communications for the datastorage system, and communications between other data storage systemsthat may be in a clustered network, such as attached to a cluster fabric215 (e.g., 106 in FIG. 1). Thus, the node 202, such as a network storagecontroller, can respond to host device requests to manage data on thedata storage device 234 (e.g., or additional clustered devices) inaccordance with these host device requests. The operating system 208 canoften establish one or more file systems on the data storage system 200,where a file system can include software code and data structures thatimplement a persistent hierarchical namespace of files and directories,for example. As an example, when a new data storage device (not shown)is added to a clustered network system, the operating system 208 isinformed where, in an existing directory tree, new files associated withthe new data storage device are to be stored. This is often referred toas “mounting” a file system.

In the example data storage system 200, memory 206 can include storagelocations that are addressable by the processors 204 and adapters 210,212, 214 for storing related software application code and datastructures. The processors 204 and adapters 210, 212, 214 may, forexample, include processing elements and/or logic circuitry configuredto execute the software code and manipulate the data structures. Theoperating system 208, portions of which are typically resident in thememory 206 and executed by the processing elements, functionallyorganizes the storage system by, among other things, invoking storageoperations in support of a file service implemented by the storagesystem. It will be apparent to those skilled in the art that otherprocessing and memory mechanisms, including various computer readablemedia, may be used for storing and/or executing application instructionspertaining to the techniques described herein. For example, theoperating system can also utilize one or more control files (not shown)to aid in the provisioning of virtual machines.

The network adapter 210 includes the mechanical, electrical andsignaling circuitry needed to connect the data storage system 200 to ahost device 205 over a network 216, which may comprise, among otherthings, a point-to-point connection or a shared medium, such as a localarea network. The host device 205 (e.g., 108, 110 of FIG. 1) may be ageneral-purpose computer configured to execute applications. Asdescribed above, the host device 205 may interact with the data storagesystem 200 in accordance with a client/host model of informationdelivery.

The storage adapter 214 cooperates with the operating system 208executing on the node 202 to access information requested by the hostdevice 205 (e.g., access data on a storage device managed by a networkstorage controller). The information may be stored on any type ofattached array of writeable media such as magnetic disk drives, flashmemory, and/or any other similar media adapted to store information. Inthe example data storage system 200, the information can be stored indata blocks on the disks 224, 226, 228. The storage adapter 214 caninclude input/output (I/O) interface circuitry that couples to the disksover an I/O interconnect arrangement, such as a storage area network(SAN) protocol (e.g., Small Computer System Interface (SCSI), iSCSI,hyperSCSI, Fiber Channel Protocol (FCP)). The information is retrievedby the storage adapter 214 and, if necessary, processed by the one ormore processors 204 (or the storage adapter 214 itself) prior to beingforwarded over the system bus 242 to the network adapter 210 (and/or thecluster access adapter 212 if sending to another node in the cluster)where the information is formatted into a data packet and returned tothe host device 205 over the network 216 (and/or returned to anothernode attached to the cluster over the cluster fabric 215).

In one embodiment, storage of information on disk arrays 218, 220, 222can be implemented as one or more storage volumes 230, 232 that arecomprised of a cluster of disks 224, 226, 228 defining an overalllogical arrangement of disk space. The disks 224, 226, 228 that compriseone or more volumes are typically organized as one or more groups ofRAIDs. As an example, volume 230 comprises an aggregate of disk arrays218 and 220, which comprise the cluster of disks 224 and 226.

In one embodiment, to facilitate access to disks 224, 226, 228, theoperating system 208 may implement a file system (e.g., write anywherefile system) that logically organizes the information as a hierarchicalstructure of directories and files on the disks. In this embodiment,respective files may be implemented as a set of disk blocks configuredto store information, whereas directories may be implemented asspecially formatted files in which information about other files anddirectories are stored.

Whatever the underlying physical configuration within this data storagesystem 200, data can be stored as files within physical and/or virtualvolumes, which can be associated with respective volume identifiers,such as file system identifiers (FSIDs), which can be 32-bits in lengthin one example.

A physical volume corresponds to at least a portion of physical storagedevices whose address, addressable space, location, etc. doesn't change,such as at least some of one or more data storage devices 234 (e.g., aRedundant Array of Independent (or Inexpensive) Disks (RAID system)).Typically the location of the physical volume doesn't change in that the(range of) address(es) used to access it generally remains constant.

A virtual volume, in contrast, is stored over an aggregate of disparateportions of different physical storage devices. The virtual volume maybe a collection of different available portions of different physicalstorage device locations, such as some available space from each of thedisks 224, 226, and/or 228. It will be appreciated that since a virtualvolume is not “tied” to any one particular storage device, a virtualvolume can be said to include a layer of abstraction or virtualization,which allows it to be resized and/or flexible in some regards.

Further, a virtual volume can include one or more logical unit numbers(LUNs) 238, directories 236, Qtrees 235, and files 240. Among otherthings, these features, but more particularly LUNS, allow the disparatememory locations within which data is stored to be identified, forexample, and grouped as data storage unit. As such, the LUNs 238 may becharacterized as constituting a virtual disk or drive upon which datawithin the virtual volume is stored within the aggregate. For example,LUNs are often referred to as virtual drives, such that they emulate ahard drive from a general purpose computer, while they actually comprisedata blocks stored in various parts of a volume.

In one embodiment, one or more data storage devices 234 can have one ormore physical ports, wherein each physical port can be assigned a targetaddress (e.g., SCSI target address). To represent respective volumesstored on a data storage device, a target address on the data storagedevice can be used to identify one or more LUNs 238. Thus, for example,when the node 202 connects to a volume 230, 232 through the storageadapter 214, a connection between the node 202 and the one or more LUNs238 underlying the volume is created.

In one embodiment, respective target addresses can identify multipleLUNs, such that a target address can represent multiple volumes. The I/Ointerface, which can be implemented as circuitry and/or software in thestorage adapter 214 or as executable code residing in memory 206 andexecuted by the processors 204, for example, can connect to volume 230by using one or more addresses that identify the one or more LUNs 238.

It may be appreciated that remote object store error handling may beimplemented for the data storage system 200. In an example, the node 202may utilize a remote object store for serving client requests. It may beappreciated that remote object store error handling may be implementedfor and/or between any type of computing environment, and may betransferable between physical devices (e.g., node 202, host device 205,a desktop computer, a tablet, a laptop, a wearable device, a mobiledevice, a storage device, a server, etc.) and/or a cloud computingenvironment (e.g., remote to the node 202 and/or the host device 205).

One embodiment of remote object store error handling is illustrated byan exemplary method 300 of FIG. 3. A storage system may provide clientswith access to client data stored within a backend. The backend may beconfigured with one or more tiers of storage. For example, the backendmay be configured with a local storage tier (e.g., solid state drives,hard disk drives, etc.), a remote object store tier (e.g., a third partystorage provider, cloud storage, etc.), etc. The storage system maystore data within the local storage tier as a performance tier forfrequently or recently accessed data because the local storage tier mayhave lower latency and more guarantees than the remote object storetier. The storage system may migrate data from the local storage tier tothe remote object store tier (e.g., less frequently or less recentlyaccessed data) or may store new data to the remote object store tier.Because the remote object store tier may not provide the same dataconsistency, validity, and/or other guarantees as the local storagetier, remote object store error handling is provided herein.

At 302, an object, into which the storage system can store data throughthe remote object store tier, is created within a remote object store.At 304, the object may be populated with a first object page comprisinga first data chunk of first data (e.g., a 4 kilobyte block of data). Inan example, the first data may be stored within the local storage tier,and may be copied/put into the object within the remote object store.The first data, such as a file, may be exported through a first volumeor other storage structure (e.g., a virtual volume (vvol), a buff treestructure, a file system structure, etc.) by the storage system forclient access.

At 306, the first object page may be populated with a first contextentry specifying a file block number or a location, of the file blocknumber for the first data chunk, within the first volume. For example,the first context entry comprises a context indicating that the fileblock number (e.g., a virtual volume block number (vvbn)) resides at aparticular location within a file system tree (e.g., a buff treestructure). In an example, the first context entry is storedsequentially after the first data chuck. In an example, the firstcontext entry is populated with checksum for the first data chunk. Thechecksum may be utilized to verify the first data chuck within theobject. In this way, the object may be formatted to comprise a first 4kilobyte block of data, a first context entry for the first 4 kilobyteblock of data, a second 4 kilobyte block of data, a second context entryfor the second 4 kilobyte block of data, etc.

At 308, a header for the object may be populated with an identifier of aname of the object and a buff tree universal identifier (buftree-uuid)of the first volume (e.g., an identifier of the file system tree). Forexample, the identifier comprises a hash of the name of the objectand/or the buftree-uuid. The identifier can be verified to ensure thatthe object is using the correct name.

In an example, a two-step put and verify operation may be performed forstoring data within the object. For example, the put operation isperformed to store the object (e.g., or to store a data chunk into anobject page within a preexisting object) to the remote object store,such as to store the first data chunk within the first object page.Responsive to the put operation completing, a verification get operationis performed to read the header of the object. The verification getoperation reads the identifier from the header and verifies theidentifier as the correct name of the object. The verification getoperation reads the buff tree universal identifier from the header andverifies the buff tree universal identifier as referring to the firstvolume. In an example where the first data was being migrated from thelocal storage tier to the remote object store as the first data chunk,the first data may be deleted based upon the verification get operationsuccessfully verify the identifier and the buff tree universalidentifier.

In an example, once the header has been verified, data corresponding toobject pages, such as the first object page, a second object page, etc.,within the object can be deleted from the local storage tier. Inparticular, there is a single transaction that writes the header, thefirst object page, the second object page, etc.

The verification get operation may be issued with a same priority (e.g.,execution priority, sending priority, etc.) as the put operation. Theverification get operation and/or the put operation may be issued with adifferent priority than client put and get operations. Thus, theverification get operation is issued to the remote object store in apath (e.g., an execution or access path) that is decoupled from a clientaccess path (e.g., a path used to send and/or process client I/Ooperations for data stored or to store within the remote object store)to the remote object store. In this way, the two-step put andverification get operation does not affect or hinder performance ofclient put and get operations.

Verification may be configured for verifying every nth object (e.g.,where n is an integer number) within the remote object store (e.g.,every 5^(th) object put into the remote object store is to besubsequently verified by a verification get operation). Upon determiningthat the object is an instance of the nth object, the two-step put andverify operation is performed. The put operation is performed to storethe object to the remote object store. The verification get operation isperformed to read the header of the object to verify the identifier andthe buff tree universal identifier.

The storage system may locally maintain a metafile for one or moreobjects within the remote object store. The metafile may be populatedwith a mapping between an object identifier to an object name derivedfrom the buff tree universal identifier and/or the sequence number. Filesystem tree pointers point to the object identifier and a slot (e.g., anoffset in the object). The name for the object may be generated basedupon the buff tree universal identifier within the metafile.Monotonically increasing sequence numbers may be assigned to objectswithin the remote object. For example, a first sequence number may beassigned to the object. The first sequence number may be stored withinthe metafile as being associated with the object.

At 310, a request for the first data may be received, such as by thestorage system from a client. In an example, the request may comprise atarget buff tree universal identifier for the first volume. The metafilemay be evaluated to determine whether the target buff tree universalidentifier matches the buff tree universal identifier within themetafile. Access is provided to the first data chunk within the objectfor satisfying the request based upon the target buff tree universalidentifier matching the buff tree universal identifier, at 312. Anoffset within the object can be used to access merely a portion of theobject, such as the first data chunk or the first object page withoutaccessing other portions of the object such as a second object page fora second data chunk. If the target buff tree universal identifier doesnot match the buff tree universal identifier, then the metafile may bedetermined as being corrupted.

Volume move operations may be performed to move the first volume from afirst location to a second location, resulting in a moved first volume.Because the buff tree universal identifier for the first volume islocally stored within the metafile (e.g., and not within the objectwithin the remote object store), the object does not need to be updatedwhen the first volume is moved. Instead, the metafile is updated with anupdated buff tree universal identifier for the moved first volume. Inthis way, bandwidth and processing resources do not need to be otherwiseconsumed with accessing the remote object store when the first volume ismoved.

In an example, a client operation timer may be specified for timing outclient operations. The client operation timer may be set to a firsttimeout value. A remote object store access timeout timer may bespecified for timing out operations to the remote object store. Theremote object store access timeout timer may be set to a second timeoutvalue that is smaller than the first timeout value. In this way, accessto the remote object store for satisfying a client access operation maybe retried one or more times based upon the remote object store accesstimeout timer timing out before the client operation timer times out.

In an example, latency of the remote object store may be monitored. Anamount of I/O throughput to the remote object store may be dynamicallyadjusted based upon the latency. For example, if the remote object storeappears to be experiencing higher than desired latency, the I/Othroughput to the remote object store may be decreased in order todecrease a load placed upon the remote object store. Otherwise, the I/Othroughput may be increased to take advantage of extra processingbandwidth of the remote object store if the latency is lower thanexpected (e.g., the remote object store has free processing bandwidth).

In an example, the storage system may be associated with multiple remoteobject stores. First latency of a first remote object store may bemonitored. Second latency of a second remote object store may bemonitored. A first amount of I/O throughput to the first remote objectstore may be dynamically adjusted based upon the first latency. A secondamount of I/O throughput to the second remote object store may bedynamically adjusted based upon the second latency. In this way,different remote object stores may be treated individually based uponhow each remote object store is performing.

In an example, monotonically increasing sequence numbers are assigned toobjects and/or object pages within the remote object store. For example,the object may be assigned a first sequence number. The first sequencenumber may be stored within the metafile for the object. The object maybe marked as invalid based upon the first sequence number becomingcorrupt or lost within the metafile. Conversely, the first sequencenumber may be marked as invalid based upon the object becoming corruptor lost.

FIG. 4 illustrates an example of a system 400 for utilizing a remoteobject store 402 as a storage tier for a storage system. The storagesystem may store objects within the remote object store 402, such as anobject 404. The object 404 may comprise a header 406. The header 406 maycomprise a version of the object 404, an indicator as to whether theobject 404 is encrypted, a creation timestamp for the object 404, a bufftree universal identifier 420 (a buftree-uuid), an identifier 418 of aname of the object 404 (e.g., a hash of the name and the buftree-uuid,which can be read back after a put operation of the object 404 or of anobject page within the object 404 to verify the hash), and/or otherinformation. In one example, the header 406 is 32 bytes or any othersize of information.

The object 404 may comprise one or more object pages corresponding todata chunks, such as data chunks derived from data moved from a localstorage tier (e.g., a performance storage tier, such as a solid statestorage tier or a disk storage tier) of the storage system to the remoteobject store 402. In one example, the object 404 may comprise space for1024 object pages, such as a first object page 408, a second object page410, and/or other object pages. The first object page 408 may comprise afirst data chunk 412 (e.g., 4 kilobytes of data or any other size ofdata) and a first context 414 associated with the first object page 408.

The first context 414 may comprise an indicator as to whether the object404 is encrypted. The first context 414 may comprise an encryption keyindex used to identify an encryption key. The first context 414 maycomprise a pseudobad indicator to indicate whether data read from thelocal storage tier had an error such as a disk error and the datacontent in the object is inconsistent. The first context 414 maycomprise an indicator as to whether a RAID or storage OS marked thepseudobad error. The first context 414 may comprise an unverified errorindicator to indicate that when data read from the local storage tierresulted in an unverified RAID error. The first context 414 may comprisea wrecked indicator that is set when data is forcefully corrupted. Thefirst context 414 may comprise a file block number (e.g., a location ofthe file block number for the first data chunk 412 within the firstvolume). The first context 414 may comprise a checksum for the firstdata chunk 412 and the first context 414. In an example, the firstcontext 414 may comprise 16 bytes of information or any other size ofinformation.

FIG. 5 illustrates an example of a system 500 for utilizing a remoteobject store 504 as a storage tier for a storage system. The storagesystem may store data, such as first data 506, with a local storage tier502 (e.g., a performance storage tier, such as a solid state storagetier). The storage system may store data, such as newly written clientdata or data from the local storage tier 502, into the remote objectstore 504 using put operations. For example, the storage system mayperform a two-step put and verify operation to move the first data 506from the local storage tier 502 into an object 508, comprising a header510 and one or more object pages, within the remote object store 504.The storage system may perform a put operation 514 to store the firstdata 506 as a first data chunk within a first object page 512 of theobject 508. Upon receiving a success response from the remote objectstore 504 for the put operation 514, a subsequent verification getoperation 516 is performed to read the header 510 and verify informationwithin the header such as an identifier (e.g., a hash of a name of theobject 508 and/or a buff tree universal identifier (buftree-uuid))and/or the buff tree universal identifier of a first volume for thefirst data chunk. Upon verifying the identifier and the buff treeuniversal identifier, the first data 506 may be deleted 518 from thelocal storage tier 502.

FIGS. 6A and 6B illustrate examples of a system 600 for utilizing aremote object store 608 as a storage tier for a storage system. Astorage system may organize client data within a volume 604 located at afirst storage location 602, as illustrated in FIG. 6A. The storagesystem may store data of the volume 604 into an object 610 of a remoteobject store 608. The storage system may maintain a metafile 606 locallyavailable to the storage system (e.g., not stored within the remoteobject store 608 that may be maintained by a third party provider). Themetafile 606 may be populated with a mapping 612 between an objectidentifier of the object 610 (e.g., file system tree pointers point tothe object identifier and an offset within the object 610) and an objectname of the object 610. When a request 616 is received from a client 614for accessing data within the object 610 (e.g., reading data from theobject 610 or writing data to the object 610), a target buff treeidentifier 618 within the request 616 is verified as matching the bufftree identifier ID within the mapping 612 of the metafile 606 forgranting access to the object 610. If the target buff tree identifier618 does not match the buff tree identifier, then the metafile 606 isdetermined as corrupt.

FIG. 6B illustrates a volume move operation 652 being performed to movethe volume 604 from the first storage location 602 to a second storagelocation 650 as a moved volume 654. The metafile 606, such as themapping 612, is updated based upon the moved volume 654 to create anupdated mapping 656. In this way, the object 610 within the remoteobject store 608 remains valid (e.g., without the need of being updated)notwithstanding the volume move operation 652.

FIG. 7 illustrates an example of a system 700 for utilizing a remoteobject store 710 as a storage tier for a storage system 704. The storagesystem 704 may monitor a latency 706 of the remote object store 710,such as latency 706 when reading from or writing to an object 712 withinthe remote object store 710. I/O throughput 708 (e.g., a number of I/Ocommands for satisfying client operations issued to the remote objectstore 710 within a certain timespan; a number of allowed pending I/Ocommands; etc.) may be dynamically adjusted based upon the latency 706.

FIG. 8 illustrates an example of a system 800 for utilizing a remoteobject store 802 as a storage tier for a storage system. The storagesystem may store objects, such as object 804, within the remote objectstore 802. The storage system may maintain a metafile 806 for objectswithin the remote object store 802. The metafile 806 may be locallymaintained by the storage system (e.g., not stored within the remoteobject store 802 that may be hosted by a third party cloud provider).The storage system may store mappings between object identifiers andobjects within the remote object store 802, such as a mapping 808 forthe object 804. The storage system may assign monotonically increasingsequence numbers to objects within the remote object store 802, such asa sequence number 810 for the object 804. Upon determining that theobject 804 has become lost, corrupt, or invalid, then storage systemmarks 814 the sequence number 810 as invalid so that the object 804 isno longer accessed.

FIG. 9 illustrates an example of a system 900 for utilizing a remoteobject store 902 as a storage tier for a storage system. The storagesystem may store objects, such as object 904, within the remote objectstore 902. The storage system may maintain a metafile 906 for objectswithin the remote object store 902. The metafile 906 may be locallymaintained by the storage system (e.g., not stored within the remoteobject store 902 that may be hosted by a third party cloud provider).The storage system may store mappings between buff tree identifiers andobjects within the remote object store 902, such as a mapping 908 forthe object 904. The storage system may assign monotonically increasingsequence numbers to objects within the remote object store 902, such asa sequence number 910 for the object 904. Upon determining that thesequence number 910 has become lost, corrupt, or invalid, the object 904may be marked as invalid 912 so that the object 904 is no longeraccessed.

Still another embodiment involves a computer-readable medium comprisingprocessor-executable instructions configured to implement one or more ofthe techniques presented herein. An example embodiment of acomputer-readable medium or a computer-readable device that is devisedin these ways is illustrated in FIG. 10, wherein the implementation 1000comprises a computer-readable medium 1008, such as a compactdisc-recordable (CD-R), a digital versatile disc-recordable (DVD-R),flash drive, a platter of a hard disk drive, etc., on which is encodedcomputer-readable data 1006. This computer-readable data 1006, such asbinary data comprising at least one of a zero or a one, in turncomprises a processor-executable computer instructions 1004 configuredto operate according to one or more of the principles set forth herein.In some embodiments, the processor-executable computer instructions 1004are configured to perform a method 1002, such as at least some of theexemplary method 300 of FIG. 3, for example. In some embodiments, theprocessor-executable computer instructions 1004 are configured toimplement a system, such as at least some of the exemplary system 400 ofFIG. 4, exemplary system 500 of FIG. 5, exemplary system 600 of FIGS.6A-6B, exemplary system 700 of FIG. 7, exemplary system 800 of FIG. 8,and/or at least some of the exemplary system 900 of FIG. 9, for example.Many such computer-readable media are contemplated to operate inaccordance with the techniques presented herein.

It will be appreciated that processes, architectures and/or proceduresdescribed herein can be implemented in hardware, firmware and/orsoftware. It will also be appreciated that the provisions set forthherein may apply to any type of special-purpose computer (e.g., filehost, storage server and/or storage serving appliance) and/orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings herein can be configured to a variety of storage systemarchitectures including, but not limited to, a network-attached storageenvironment and/or a storage area network and disk assembly directlyattached to a client or host computer. Storage system should thereforebe taken broadly to include such arrangements in addition to anysubsystems configured to perform a storage function and associated withother equipment or systems.

In some embodiments, methods described and/or illustrated in thisdisclosure may be realized in whole or in part on computer-readablemedia. Computer readable media can include processor-executableinstructions configured to implement one or more of the methodspresented herein, and may include any mechanism for storing this datathat can be thereafter read by a computer system. Examples of computerreadable media include (hard) drives (e.g., accessible via networkattached storage (NAS)), Storage Area Networks (SAN), volatile andnon-volatile memory, such as read-only memory (ROM), random-accessmemory (RAM), electrically erasable programmable read-only memory(EEPROM) and/or flash memory, compact disk read only memory (CD-ROM)s,CD-Rs, compact disk re-writeable (CD-RW)s, DVDs, cassettes, magnetictape, magnetic disk storage, optical or non-optical data storage devicesand/or any other medium which can be used to store data.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter defined in the appended claims is not necessarilylimited to the specific features or acts described above. Rather, thespecific features and acts described above are disclosed as exampleforms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

Furthermore, the claimed subject matter is implemented as a method,apparatus, or article of manufacture using standard application orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer application accessible from anycomputer-readable device, carrier, or media. Of course, manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

As used in this application, the terms “component”, “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentincludes a process running on a processor, a processor, an object, anexecutable, a thread of execution, an application, or a computer. By wayof illustration, both an application running on a controller and thecontroller can be a component. One or more components residing within aprocess or thread of execution and a component may be localized on onecomputer or distributed between two or more computers.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B and/or the like generally means A orB and/or both A and B. Furthermore, to the extent that “includes”,“having”, “has”, “with”, or variants thereof are used, such terms areintended to be inclusive in a manner similar to the term “comprising”.

Many modifications may be made to the instant disclosure withoutdeparting from the scope or spirit of the claimed subject matter. Unlessspecified otherwise, “first,” “second,” or the like are not intended toimply a temporal aspect, a spatial aspect, an ordering, etc. Rather,such terms are merely used as identifiers, names, etc. for features,elements, items, etc. For example, a first set of information and asecond set of information generally correspond to set of information Aand set of information B or two different or two identical sets ofinformation or the same set of information.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method comprising: creating an object within aremote object store; populating the object with a first object pagecomprising a first data chuck of first data from a local storage tier,wherein the first data is exported for client access through a firstvolume; populating the first object page with a first context entryspecifying a location, of a file block number for the first data chunk,within the first volume; populating a header for the object with anidentifier of a name of the object and a buff tree universal identifierof the first volume; receiving a request for the first data; andproviding the first data chuck from the object within the remote objectstore in response to the request.
 2. The method of claim 1, wherein thepopulating comprises: performing a two-step put and verify operation,comprising: performing a put operation to store the object to the remoteobject store; and performing a verification get operation to read theheader of the object to verify the identifier as the name of the objectbased upon completion of the put operation.
 3. The method of claim 1,wherein the populating comprises: performing a two-step put and verifyoperation, comprising: performing a put operation to store the object tothe remote object store; and performing a verification get operation toread the header of the object to verify the buff tree universalidentifier is for first volume.
 4. The method of claim 2, wherein theperforming a verification get operation comprises: issuing theverification get operation with a same priority as the put operation. 5.The method of claim 2, wherein the performing a verification getoperation comprises: issuing the verification get operation with adifferent priority than client put and get operations, wherein theverification get operation is issued to the remote object store in apath that is decoupled from a client access path to the remote objectstore.
 6. The method of claim 1, comprising: specifying that every nthobject within the remote object store is to be verified; determiningthat the first object is an instance of the nth object; and performing atwo-step put and verify operation, comprising: performing a putoperation to store the object to the remote object store; and performinga verification get operation to read the header of the object to verifythe identifier and the buff tree universal identifier.
 7. The method ofclaim 1, wherein the object comprises a first object page and a secondobject page, the method comprising: accessing the first object page,without access the second object page, within the object using an offsetassociated with first object page.
 8. The method of claim 1, comprising:populating the first context entry with a checksum for the first datachunk and the first context entry; and utilizing the checksum to verifythe first data chuck within the object.
 9. A non-transitory machinereadable medium comprising instructions for performing a method, whichwhen executed by a machine, causes the machine to: maintain an objectwithin a remote object store, the object comprising: a first object pagecomprising: a first data chuck of first data from a local storage tier,wherein the first data is exported for client access through a firstvolume; and a first context entry specifying a location, of a file blocknumber for the first data chunk, within the first volume; and a headerwith an identifier of a name of the object and a buff tree universalidentifier of the first volume; populate a metafile with a mappingbetween the buff tree universal identifier and the object; receive arequest for the first data, wherein the request comprises a target bufftree universal identifier for the first volume; and provide access tothe first data chunk within the object for the request based upon thetarget buff tree universal identifier matching the buff tree universalidentifier within the metafile.
 10. The non-transitory machine readablemedium of claim 9, wherein the instructions cause the machine to:determine that the metafile is corrupt based upon the target buff treeuniversal identifier not matching the buff tree universal identifierwithin the metafile.
 11. The non-transitory machine readable medium ofclaim 9, wherein the instructions cause the machine to: generate thename for the object based upon buff tree universal identifier within themetafile.
 12. The non-transitory machine readable medium of claim 9,wherein the instructions cause the machine to: assign monotonicallyincreasing sequence numbers to objects within the remote object store,wherein the object is assigned a first sequence number; and storage thefirst sequence number within the metafile.
 13. The non-transitorymachine readable medium of claim 9, wherein the instructions cause themachine to: perform a volume move operation for the first volume to movethe first volume from a first location to a second location resulting ina moved first volume; and update the metafile with an updated buff treeuniversal identifier for the moved first volume.
 14. The non-transitorymachine readable medium of claim 9, wherein the instructions cause themachine to: perform a two-step put and verify operation, comprising:performing a put operation to store the object to the remote objectstore; and performing a verification get operation to read the header ofthe object to verify the identifier and the buff tree universalidentifier; and delete the first data from the local storage tier basedupon the verification get operation successfully verifying theidentifier and the buff tree universal identifier.
 15. A computingdevice comprising: a memory containing machine readable mediumcomprising machine executable code having stored thereon instructionsfor performing a method; and a processor coupled to the memory, theprocessor configured to execute the machine executable code to cause theprocessor to: perform a two-step put and verify operation, comprising:creating an object within a remote object store; populating the objectwith a first object page comprising a first data chuck of first datafrom a local storage tier, wherein the first data is exported for clientaccess through a first volume; populating the first object page with afirst context entry specifying a location, of a file block number forthe first data chunk, within the first volume; populating a header forthe object with an identifier of a name of the object and a buff treeuniversal identifier of the first volume; and performing a verificationget operation to read the header of the object to verify the identifierand the buff tree universal identifier
 16. The computing device of claim15, wherein the machine executable code causes the processor to: specifya client operation timeout timer, for timing out client operations, tohave a first timeout value; and specify a remote object store accesstimeout timer, for timing out operations to the remote object store, tohave a second timeout value smaller than the first timeout value. 17.The computing device of claim 16, wherein the machine executable codecauses the processor to: specify a second remote object store accesstimeout timer, for timing out operations to a second remote objectstore, to have a third timeout value different than the second timeoutvalue.
 18. The computing device of claim 15, wherein the machineexecutable code causes the processor to: monitor latency of the remoteobject store; and dynamically adjust an amount of I/O throughput to theremote object store based upon the latency.
 19. The computing device ofclaim 15, wherein the machine executable code causes the processor to:monitor first latency of the remote object store; monitor second latencyof a second remote object store; dynamically adjust a first amount ofI/O throughput to the remote object store based upon the first latency;and dynamically adjust a second amount of I/O throughput to the remoteobject store based upon the second latency.
 20. The computing device ofclaim 15, wherein the machine executable code causes the processor to:assign monotonically increasing sequence numbers to objects within theremote object store, wherein the object is assigned a first sequencenumber; mark the object as invalid based upon the first sequence numberbecoming corrupt or lost; and mark the first sequence number as invalidbased upon the object becoming corrupt or lost.